Atmospheric Signals Recorded by Seismometers in the Sub-Seismic Frequency Band

Broadband seismometers, though designed to record ground motion generated by earthquakes, are also sensitive to a wide range of other processes occurring at the interface between the solid Earth, oceans, and atmosphere, often considered noise. In the sub-seismic band (1–24 hours), they can detect tidal signals but are limited by self-noise for weaker Earth and atmospheric processes. By applying a coherence-based network stacking technique to large seismic arrays, we identify weak, periodic gravity signals at these frequencies. Using three years of collocated vertical seismic and pressure data from USArray, we demonstrate the atmospheric origin of these oscillations. Coherence and transfer function analysis reveal strong links between pressure and seismic acceleration at atmospheric tide periods. The transfer function shows frequency dependence consistent with superconducting gravimeter observations, and its consistently negative phase indicates that pressure increases correspond to decreases in gravitational acceleration. This confirms Newtonian attraction from atmospheric mass changes as the dominant mechanism. Our results show that network stacks of broadband seismometers can detect atmospheric gravity variations as small as 10–100 nanogals, demonstrating their value for gravimetry and for observing atmospheric dynamics. This approach also provides a framework to estimate atmospheric noise in the sub-seismic range, improving the detection of solid Earth signals once such contamination is removed.